1. Field of Use
This invention relates generally to ink dams for printing presses. In particular, it relates to a flexographic multicolor printing press wherein the ink fountain has means for applying different colored inks to different sections of a circumferentially grooved fountain roll for subsequent transfer to an anilox roll, printing cylinder, and moving web and wherein ink dams or dividers, each having a hole through which the fountain roll extends, divide the ink fountain into separate ink compartments and cooperate with the fountain and anilox rolls to prevent ink transfer between adjacent sections on each roll.
2. Description of the Prior Art
Some flexographic printing presses include an ink fountain having means to apply ink to a fountain roll for subsequent transfer to an anilox roll, printing cylinder, and moving web. Typically, the ink fountain extends substantially the entire length of the rolls in the press. If it is desired to print using inks of different colors across the web, or to print on a web which is narrower than the length of the ink fountain, it is the practice to divide the fountain into separate compartments by means of ink dams or dividers which are constructed so as to divide the fountain into separate compartments, to maintain a fluid-tight seal between compartments in the fountain, and to maintain a seal against the fountain roll. The prior art contains numerous examples of such dividers and the following U.S. Pat. Nos. illustrate the state of the art: 3,831,517; 3,635,161; 2,887,050; 2,525,363; and 2,442,700.
In some prior art arrangements, the ink dam or divider has edges confronting the fountain roll and the floor of the ink fountain pan and resilient sealing means are disposed along the edge confronting the fountain roll to form a seal. One of the difficulties with such prior art arrangements is that the friction between the fountain roll and the sealing means eventually results in wearing down of the sealing means thereby allowing ink to leak past the sealing means thereby contaminating ink in an adjacent compartment or allowing ink to be applied to a section of the roll whereat it is not desired. This problem is aggravated in certain industries where inks of very low viscosity, almost as thin as water, are employed. Prior art attempts to overcome this problem have not always been successful, and consequently, it is necessary in some industries to avoid the problem entirely by turning to different methods of producing printed material.
For example, in the manufacture of paper toweling, it has heretofore been the practice to imprint a relatively wide web of material (on the order of eight to ten feet wide) in a flexographic printing press which applies spaced apart bands or designs of the same color on the web and then to subsequently split the web and form separate rolls of paper toweling each having the same color imprinted thereon. A separate press (or the same press set up for a different colored ink) is then used to produce rolls of paper toweling of other colors. Manual labor is then employed to select rolls of different colors and pack them in a shipping container whereby the purchaser has a selection of different colored rolls available. This procedure is time-consuming and costly.